It sounds like your issue is on the digital interface on the receive side. You might want to try changing the clock polarity on the McBSP for the receive side. If the McBSP is trying to read the data on the exact same edge that the AIC23 is writing the data then you run into a problem where sometimes it gets the correct bit and other times it doesn't. This can cause the crackling you describe.
You might also want to make sure you have the correct offset/delay specified. If the AIC23 is in I2S mode then make sure you have a 1-bit delay programmed. I've seen similar issues with this too. In this particular case usually the audio will sound fine if the input audio is less than half of the full-scale range and it will distort when you go over (since you're effectively left-shift the data by one by having the wrong offset). It sounds more like the polarity from what you describe but you might want to check this as well. Brad ________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Sneha Shah Sent: Friday, September 21, 2007 8:39 AM To: [EMAIL PROTECTED] Cc: [email protected] Subject: AIC23 codec related query Hi, We are running audio loop back application on DM6446 using AIC23 codec, but we are able to here some noise with the song. Following point elaborates type and form of noise 1. Noise is of crackling type when heard. 2. The noise is not continuous. It is very much random in nature. 3. It is being heard in both the channels Following are the things that we did in order to remove it. 1. Experiment : We Configured AIC23 registers with below configuration ADDRESS REGISTER Register address Register Description Register Value 0000000 Left line input channel volume control 0x17 0000001 Right line input channel volume control 0x17 0000010 Left channel headphone volume control 0x1F9 0000011 Right channel headphone volume control 0x1F9 0000100 Analog audio path control 0x12 0000101 Digital audio path control 0x01 0000110 Power down control 0x00 0000111 Digital audio interface format 0x12 0001000 Sample rate control 0x18 0001001 Digital interface activation 0x01 0001111 Reset register 0x00 Pls note that AIC23 is configured as slave and McBSP is Master. Also, Clock Mode is NORMAL Mode. Result: No improvement 2. Experiment: Configured AIC23 in Bypass mode by setting Bypass bit in Analog audio path Control to 1 Results: Was able to play song successfully without any crackling noise. 3. Experiment: Checked receive buffer in driver for any garbage value. The noise can be very well observed in the buffer at driver level only. Reslult: the receive buffer contains noise which depicts that noise is originated well at the lower levels. 4. Experiment: Clock settings Result: BCLK - 1MHz for 32K stereo mode LRCIN - 32 KHz LRCOUT- 32 KHz MCLK- 12.288 MHz Note: When executing Player application(reading a file and playing it at respective sampling rate), it is observed that noise does not exists. It will be great if you can help me to reduce the noise. Thank you in advanced. Thanks, [Sneha Shah]
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